Thermoplastic copolyester elastomers in which the polyester is modified with long rubbery segments have long been known in the art and are used in the preparation of molded and extruded articles. Such resins can be used alone or in conjunction with fillers or other resins to provide materials having a variety of properties. It is well known, however, that materials of this general type are subject to thermal degradation. U.S. Pat. No. 3,023,192, 3,651,014, 3,766,146, 3,784,520 and 3,763,109 are among prior patents describing elastomers of this type.
Unstabilized elastomers of the type described above exhibit poor processing behavior and unacceptable performance, especially at elevated temperatures. While a number of antioxidant stabilizers are available for use in polymers, many are unsuitable for use in copolyester elastomers of the type mentioned above because of the severe time-temperature conditions involved in the manufacture and/or use in such elastomers. When used in elastomers of this type, most available stabilizers either inhibit polymer formation or result in production of a non-white colored product. Additionally most available stabilizers do not provide adequate long term retention of desirable mechanical and thermal properties. U.S. Pat. Nos. 4,355,155 and 4,405,749 describe elastomer of the general type described above but which is modified to provide improved thermal stability together with a desirable white color.